Fuel injection

ABSTRACT

A fuel injector, in particular for the direct injection of fuel into the combustion chamber of a mixture-compressing, externally fired internal combustion engine, comprising, upstream from a valve-seat surface, a swirl disk provided with swirl channels from which, given an open fuel injector, the fuel flows with a circumferential speed into a swirl chamber which is also located upstream from the valve-seat surface. Each point downstream from the swirl disk ( 35 ) through which a flow is to pass has a larger extension in every spatial direction than the diameter of the swirl channels.

FIELD OF THE INVENTION

The present invention relates to a fuel injector.

BACKGROUND INFORMATION

Fuel injectors which are provided with a disk with fuel channels forguiding a valve-closure member and for generating a swirl in the fuelflow are described in German Patent Application No. DE 36 43 523. Thefuel channels have a tangential component, which imparts acircumferential component to the velocity vector of the flow. The flowcross-section, which is open across the entire cross-section of the fuelchannel, has a restricting effect on the flow rate. Throttling the flowcauses a pressure decrease at the disk, which is utilized to form asealing surface pressure and to avoid a secondary flow path. Fuelmetering and swirl generation occur upstream from the sealing seat. Withthe aid of a bore introduced in the center of the disk, thevalve-closure member, and the valve needle, respectively, are alsoradially guided, the tolerance of the gap formed between the valveneedle, or the valve-closure member, being chosen so as to obtain anhydraulically sealing fit.

Another fuel injector is described in German Patent Application No. DE196 25 059, where the metering of the fuel quantity and the formation ofa swirl-imparted flow also occur upstream from the sealing seat. In thiscase, the fuel channels, which are used to meter the fuel, are designedeither as bores or as grooves, the grooves being closed by thevalve-seat surface to form swirl channels.

Both of the above-described fuel injectors have fuel channels whosecross-section determines the metering of a specific fuel quantity.Simultaneously, the tangential components of the fuel channels produce aswirl in the fuel flow. Observing tight tolerances when introducing theflow channels is thus of paramount importance for the precise meteringof the fuel quantity to be injected. This makes the manufactureexpensive, which is a disadvantage.

Another disadvantage of the mentioned fuel injectors is the strongresponse to contamination of the channels. A modification of thecross-section as a result of contaminated channels causes a change inthe metered quantity and, due to the swirl generation, a change in thejet angle as well.

Moreover, the possible deposition of dirt particles contained in thefuel in the area of the valve-sealing seat is also disadvantageous.Deposits formed in the area of the valve-sealing seat prevent a completeclosing of the fuel injector and, in this way, may allow the escape of asmall quantity of fuel after the spray-off process has been concluded. Adegraded mixture formation and combustion are the result.

SUMMARY

A fuel injector according to an example embodiment of the presentinvention, may have the advantage that dirt particles that are carriedthrough the swirl channels by the fuel flow have no opportunity tosettle along the further flow route. The swirl channels constitute thenarrowest dimension of the flow route to the spray-off orifice, so thata contamination of the sealing seat is prevented.

The small diameter of the individual swirl channels acts as a filter forany dirt particles present in the fuel flow. The dirt particles arefiltered out at the upstream side of the swirl disk.

Also advantageous is the minimal effect a contamination of individualswirl channels has on the swirl formation. The clogging that may occurat the upstream side of the swirl disk by filtering out dirt particlesthat are carried along, reduces the entire unobstructed flowcross-section only to a minimal extent. The effect on the swirlgeneration is negligible.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the present invention is represented insimplified form in the drawing and elucidated in more detail in thefollowing description.

FIG. 1 shows a schematic partial section through an exemplary embodimentof a fuel injector according to the present invention.

FIG. 2 shows a schematic part-section of a detail II of FIG. 1 throughthe example embodiment of the fuel injector with a contact surface inthe axial direction.

FIG. 3 shows a view of the upstream side of a swirl disk of theexemplary embodiment of the fuel injector.

DETAILED DESCRIPTION

Before an exemplary embodiment of a swirl disk of a fuel injector 1according to the present invention is described more precisely with theaid of FIGS. 2 and 3, to better understand the present invention, fuelinjector 1 is briefly explained in an overall representation withrespect to its main components, on the basis of FIG. 1.

Fuel injector 1 is designed in the form of an injector forfuel-injection systems of mixture-compressing internal combustionengines with externally supplied ignition. Fuel injector 1 isparticularly suitable for the direct injection of fuel into a combustionchamber (not shown) of an internal combustion engine.

Fuel injector 1 includes a nozzle body 2, in which a valve needle 3 ispositioned. Valve needle 3 is in operative connection with avalve-closure member 4 that cooperates with a valve-seat surface 6,arranged on a valve-seat member 5, to form a sealing seat. In theexemplary embodiment, fuel injector 1 is an inwardly opening,electro-magnetically actuable fuel injector 1 which has aspray-discharge orifice 7. Nozzle body 2 is sealed from external pole 9of a magnetic coil 10 by a seal 8. Magnetic coil 10 is encapsulated in acoil housing 11 and wound on a bobbin 12, which lies adjacent to aninternal pole 13 of magnetic coil 10. Internal pole 13 and external pole:9 are separated from each other by a gap 26 and are supported on aconnecting component 29. Magnetic coil 10 is energized via an electricline 19 by an electric current, which can be supplied via an electricalplug-in contact 17. Plug-in contact 17 is enclosed in a plastic jacket18, which may be sprayed onto internal pole 13.

Valve needle 3 is guided in a valve needle guide 14, which is designedas a disk. A paired adjustment disk 15 adjusts the (valve) lift. On theother side of adjustment disk 15 is an armature 20. It is connected byforce-locking to valve needle 3 via a first flange 21, and valve needle3 is connected to first flange 21 by a welded seam 22. Braced againstvalve needle 21 is a return spring 23 which, in the present design offuel injector 1, is prestressed by a sleeve 24.

Fuel channels 30 a and 30 b run in valve-needle guide 14 and in armature20. A filter element 25 is disposed in a central fuel supply 16. Fuelinjector 1 is sealed from a distributor line (not shown) by a gasket 28.

In the rest position of fuel injector 1, return spring 23, via flange 21at valve needle 3, acts upon armature 20 counter to its lift directionin such a way that valve-closure member 4 is retained in sealing contactagainst valve-seat surface 6. Magnetic coil 10, upon excitation,generates a magnetic field which moves armature 20 in the liftdirection, counter to the spring force of return spring 23, the liftbeing specified by a working gap 27 existing in the rest positionbetween internal pole 13 and armature 20. Armature 20 also carries alongin the lift direction first flange 21, which is welded to valve needle3, and thus valve needle 3. Valve-closure member 4, being operativelyconnected to valve needle 3, lifts off from valve seat surface 6, andfuel reaching spray-orifice 7 via swirl channels 36 is sprayed off.

When the coil current is turned off, armature 20 falls away frominternal pole 13 once the magnetic field has decayed sufficiently, dueto the pressure of restoring spring 23 on first flange 21, whereuponvalve needle 3 moves in a direction counter to the lift. As a result,valve-closure member 4 comes to rest on valve-seat surface 6, and fuelinjector 1 is closed.

FIG. 2, in a part-sectional view, shows an exemplary embodiment of swirldisk 35 with adjacent swirl chamber 37 of a fuel injector 1 according tothe present invention.

Swirl disk 35 is in the form of a disk and is fixed in a cylinder-shapedrecess 40 of valve-seat member 5. Swirl disk 35 may be mounted bypressing it into valve-seat member 5, for instance. A gap, forming aswirl chamber 37, remains in the axial direction between valve-seatmember 5 and swirl disk 35. Swirl disk 35 has a central bore 38 forguiding valve-closure member 4. Relative to the diameter ofvalve-closure member 4, bore 38 is toleranced so as to prevent a gapfrom forming as a secondary flow path for the fuel between valve-closuremember 4 and swirl disk 35.

To guide the flow, a plurality of swirl channels 36 is introduced inswirl disk 35 whose center axes 41 may be inclined at identical ordifferent angles with respect to center axis 42 of fuel injector 1. Whenfuel injector 1 is open, the fuel flows through swirl channels 36 intoswirl chamber 37. There it will receive a circumferential speed, due toa tangential component of swirl channels 36. The swirl of the fuelgenerated in this manner causes the fuel to be sprayed off onto acone-shaped shell whose opening angle is a function of the swirlgenerated in swirl chamber 37. Swirl chamber 37 has a cylinder shape andits height is bounded by valve-seat member 5 and swirl disk 35.

The diameter of swirl channels 36 is smaller than the diameter of thedirt particles present in the fuel. Swirl disk 35 thus supplements thefunction of filter 25. At the same time, the entire cross-section of theswirl channels is able to specify the metered fuel quantity for thecompletely open fuel injector.

The height of swirl chamber 37 is specified by a stop 39. Swirl disk 35is inserted into valve-seat member 5 until it makes contact with stop39. Stop 39, may be in the form of an annular shoulder reaching intocylindrical recess 40 of valve-seat member 5 and, at the same time,forms the radial boundary of swirl chamber 37. The inner diameter ofannular shoulder 39 is just large enough to allow the downstream side ofswirl channels 36 to discharge into swirl chamber 37.

Valve-closure member 4 has a preferably spherical geometry on its sideforming the sealing seat, and remains in sealing contact with valve-seatmember 5 when valve needle 3 is inclined relative to the center axis offuel injector 1.

FIG. 3 shows an upstream view of swirl disk 35. Swirl channels 36 arearranged on two concentric hole circles, for instance. Center axes 41 ofswirl channels 36 are preferably equidistant along the periphery of therespective hole circle and, run in an inclined yet parallel manner withrespect to each other relative to the center axis of fuel. injector 1.

A single swirl channel 36 forms the most narrow point for theflow-through along the flow route of the fuel to spray-off orifice 7.Downstream from swirl channel 35, the smallest extension of the flowpath is greater in each spatial direction than the diameter of a singleswirl channel 36. Therefore, valve-closure member 4 especially lifts offto such an extent that the gap formed between lifted-off valve-closuremember 4 and valve-seat surface 6, extending in the radial directionfrom the center point of spherical valve-closure member 4, is greater atits most narrow point than the diameter of the most narrow swirl channel36. In this way, it is prevented that dirt particles, which are carriedthrough swirl channels 36 by the fuel flow, deposit in the area of swirlchamber 37 or the valve-sealing seat. Preferably, the diameter of swirlchannels 36 is smaller than the opening lift at which valve-closuremember 4 lifts off from valve-seat surface 6 during the openingmovement. In this way it is ensured that tiny dirt particles are heldback from swirl disk 35 if they are larger than the opening lift.Contamination and blockage of the sealing seat are thus prevented.

In this manner, the sealing function of valve-closure member 4 andcorresponding valve-seat surface 6 is ensured over the service life offuel injector 1.

Swirl channels 36 may be introduced, for instance, by laser drilling orby micro-eroding. Swirl channels 36 are preferably introduced beforeswirl disk 35 is hardened and the guide play is ground.

What is claimed is:
 1. A fuel injector for a fuel-injection system of aninternal combustion engine, comprising: a valve-seat member providedwith a valve-seat surface; a valve closure member, the valve-seatsurface cooperating with the valve-closure member to form a sealingseat; a swirl disk provided with swirl channels having a tangentialcomponent for generating swirl, the swirl disk being disposed upstreamfrom the valve-seat surface of the valve-seat member; and a swirlchamber formed between the swirl disk and the valve-seat member; whereina minimal extension of flow paths arranged downstream from the swirldisk is greater in every spatial direction than a smallest diameter ofeach swirl channel in the swirl disk.
 2. The fuel injector according toclaim 1, wherein a diameter of the swirl channels is smaller than adiameter of dirt particles that are present in fuel in the fuelinjector.
 3. The fuel injector according to claim 1, wherein the swirlchannels are disposed on a plurality of concentric hole circles.
 4. Thefuel injector according to claim 1, wherein each of the swirl channelshas a different diameter.
 5. The fuel injector according to claim 1,wherein each of the swirl channels has a different orientation.
 6. Thefuel injector according to claim 1, wherein the swirl disk has at least100 swirl channels.
 7. The fuel injector according to claim 1, whereinthe swirl channels are introduced into the swirl disk by laser drilling.8. The fuel injector according to claim 1, wherein the swirl channelsare introduced into the swirl disk by micro-erosive machining.
 9. Thefuel injector according to claim 1, wherein the smallest diameter ofeach swirl channel is smaller than an opening lift at which thevalve-closure member lifts off from the valve-seat surface during anopening movement.
 10. The fuel injector according to claim 1, wherein adiameter of the swirl channels is smaller than a diameter of dirtparticles that are present in fuel in the fuel injector, and the swirlchannels are disposed on a plurality of concentric hole circles.
 11. Thefuel injector according to claim 10, wherein each of the swirl channelshas a different diameter.
 12. The fuel injector according to claim 11,wherein each of the swirl channels has a different orientation.
 13. Thefuel injector according to claim 10, wherein the swirl disk has at least100 swirl channels.
 14. The fuel injector according to claim 12, whereinthe swirl channels are introduced into the swirl disk by laser drilling.15. The fuel injector according to claim 12, wherein the swirl channelsare introduced into the swirl disk by micro-erosive machining.
 16. Thefuel injector according to claim 12, wherein the smallest diameter ofeach swirl channel is smaller than an opening lift at which thevalve-closure member lifts off from the valve-seat surface during anopening movement.
 17. The fuel injector according to claim 10, whereinthe smallest diameter of each swirl channel is smaller than an openinglift at which the valve-closure member lifts off from the valve-seatsurface during an opening movement.
 18. The fuel injector according toclaim 1, wherein relative to a diameter of the valve-closure member, abore is toleranced to prevent a gap from forming as a secondary flowpath for the fuel between valve-closure member and the swirl disk. 19.The fuel injector according to claim 1, wherein the swirl disk hascenter axes that are inclined at one of identical and different angleswith respect to a center axis of the fuel injector.
 20. The fuelinjector according to claim 1, wherein the swirl chamber has a cylindershape and its height is bounded by the valve-seat member and the swirldisk.
 21. The fuel injector according to claim 1, wherein an entirecross-section of the swirl channels is able to specify a metered fuelquantity when the fuel injector is completely open.
 22. The fuelinjector according to claim 1, wherein a height of the swirl chamber isspecified by a stop, and the swirl disk is insertable into thevalve-seat member until it contacts the stop.
 23. The fuel injectoraccording to claim 22, wherein the stop includes an annular shoulderreaching into a cylindrical recess of the valve-seat member and forms aradial boundary of the swirl chamber.
 24. The fuel injector according toclaim 23, wherein an inner diameter of the annular shoulder is justlarge enough to allow a downstream side of the swirl channels todischarge into the swirl chamber.
 25. The fuel injector according toclaim 1, wherein the valve-closure member has a spherical geometry onits side forming the sealing seat, and remains in sealing contact withthe valve-seat member when the valve needle is inclined relative to acenter axis of the fuel injector.
 26. The fuel injector according toclaim 1, wherein center axes of the swirl channels are equidistant alonga periphery of a respective hole circle, and run in an inclined andparallel manner with respect to each other relative to a center axis ofthe fuel injector.
 27. The fuel injector according to claim 1, whereinthe valve-closure member lifts off to such an extent that a gap formedbetween a lifted-off valve-closure member and a valve-seat surface,extending in a radial direction from a center point of the valve-closuremember 4, is greater at its most narrow point than a diameter of a mostnarrow swirl channel, so as to prevent dirt particles, which are carriedthrough the swirl channels by fuel flow, from depositing in an area ofthe swirl chamber or the valve-sealing seat.
 28. The fuel injectoraccording to claim 27, wherein a diameter of the swirl channels issmaller than an opening lift at which the valve-closure member lifts offfrom the valve-seat surface during an opening movement, so that at leastsome dirt particles are held back from the swirl disk if they are largerthan the opening lift.